1. Field of the Invention
The present invention relates to a pneumatic tire suitable for winter use, and more specifically relates to a pneumatic tire that has improved on-ice performance and on-snow performance and good balance.
2. Background Information
A pneumatic tire for winter use such as a studless tire conventionally has the following configuration. Multiple longitudinal grooves extending in a tire circumferential direction and multiple lateral grooves extending in a tire width direction are provided in a tread portion, and these longitudinal and lateral grooves define multiple blocks. Multiple sipes extending in the tire width direction are provided in each of the blocks (see Japanese patent application Kokai publication No. 2009-96220, for example).
Such a pneumatic tire for winter use requires both on-ice performance and on-snow performance. Generally, when the on-ice performance is to be improved, such a tread pattern is used that a ratio of groove area in the tread portion is reduced to increase an actual contact area. However, merely reducing the ratio of groove area in the tread portion causes reduction in on-snow performance. In other words, there is a trade-off relationship between the on-ice performance and the on-snow performance, and it is extremely difficult to achieve both performances in good balance.